Abstract
Anoxybacillus kamchatkensis NASTPD13 used herein as a source for thermostable alkaline xylanase were isolated from Paudwar Hot Springs, Nepal. NASTPD13 cultured at 60°C, pH 7 and in presence of inorganic (ammonium sulfate) or organic (yeast extract) nitrogen sources, produced maximum xylanase enzyme. Xylanase production in the cultures was monitored by following the ability of culture media to hydrolyze beech wood xylan producing xylooligosaccharide and xylose by thin layer chromatography (TLC). The extracellular xylanase was isolated from optimized A. kamchatkensis NASTPD13 cultures by ammonium sulfate (80%) precipitation; the enriched xylanase preparation was dialyzed and purified using Sephadex G100 column chromatography. The purified xylanaseshowed 11-fold enrichment with a specific activity of 33 U/mg and molecular weight were37 kDa based on SDS-PAGE and PAGE-Zymography. The optimum pH and temperature of purified xylanase was 9.0 and 65°C respectively retainingmore than 50% of its maximal activity over a broad range of pH (6–9) and temperature (30–65°C). With beech wood xylan, the enzyme showed Km 0.7 mg/ml and Vmax 66.64 μM/min/mg The xylanase described herein is a secretory enzyme produced in large quantities by NASTPD13 and is a novel thermostable, alkaline xylanase with potential biotechnological applications.
Highlights
Lignocellulose,a major source of renewable organic matter, is mainly comprised ofof lignin, hemicellulose, and cellulose (Mmango-Kaseke et al, 2016)
Given the results described we are confident that this is the first study of its kind that reports the isolation and characterization of novel xylanase from A. kamchatkensis NASTPD13
Based on biochemical, morphological characteristics and 16S rDNA sequences A. kamchatkensis NASTPD13 was identified as A. kamchatkensis and designated as A. kamchatkensis NASTPD13 and the16S rDNA sequence was submitted to Gene Bank (Accession No KY373247)
Summary
Lignocellulose,a major source of renewable organic matter, is mainly comprised ofof lignin, hemicellulose, and cellulose (Mmango-Kaseke et al, 2016). The lignocellulose is mainly obtained from agriculture, horticulture and forest waste, paper-pulp,timber and other agro-forest allied industries. Such lignocelluloses waste can potentially be utilized into various value-added products such as biofuels like bioethanol and biochemical products. Synergistic action of several enzymes are required for complete degradation of hemicellulose to pentose sugar, namely endoxylanases (endoβ- 1,4-xylanase), β-xylosidases (xylan 1,4-β-xylosidase), and α- glucuronidases (α-glucosiduronase) and side-chain cleaving enzymes: α-L-arabinofuranosidase, feruloyl esterase, and acetyl xylan esterase that produces xylooligomers which are further degraded to monomeric sugar xylose by β-D-xylosidases (Ellis and Magnuson, 2012; Sun et al, 2012; Motta et al, 2013). Xylanase plays a critical role in the degradation of hemicellulose, has many industrial applications, e.g., bio-conversion of lignocellulosic materials to fermentable substrates in biofuel industries (Podkaminer et al, 2012; Roy et al, 2013)
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